1. Field of the Invention
This invention relates to high explosives, capable of detonation, constructed by uniformly mixing components of differing chemical and physical properties in order to take advantage of the functions performed by these different components. More specifically, the invention relates to explosive charges in which the chemical and physical composition changes gradually from point to point in order to accomplish differing, specific design objectives, including performing multiple tasks equally well.
2. Description of the Related Art
Generally, an explosive charge is designed to accomplish a specific task. The particular chemical composition of the explosive is chosen from several candidates to perform the task best. If none of the candidates can alone perform the task well, several chemical compositions are uniformly mixed together in the same explosive. For example, an explosive charge mostly composed of HMX (Cyclotetramethylenetetranitramine) is good for fragmenting metal cases and driving the fragments at high velocity, but it will perform less than optimum in internal blast applications. That is because to drive fragments well, the explosive has to release a large amount of gases fast, but a good internal blast explosive has to be rich in fuels that react with the air contained inside the target, an intrinsically slow process. HMX and Al (Aluminum) particles can be uniformly mixed to create a good internal blast explosive.
Charges in which two or three different explosives are combined in a single charge or warhead have also been constructed. For example, a plane-wave generator is a charge shaped like a truncated cone the core of which is constructed of an explosive in which the detonation propagates at moderate velocity, but the outer layer is made of an explosive in which the detonation propagates at a significantly higher velocity. The angle of the cone is adjusted according to the ratio of the two detonation velocities to produce a plane or flat detonation wave profile. An example in which more than one charge are combined in the same warhead is explosive trains. For safety reasons, the main charge of a warhead has to be made of an insensitive explosive composition. In order to initiate the warhead successfully, a small detonator made of sensitive energetic material ignites a booster charge made of an explosive less sensitive than the detonator, but capable of generating large pressures capable of initiating the insensitive, hard-to-initiate main charge.
However, problems arise when combining two or more explosives into a single charge. At each interface between two different explosives, sudden changes in acoustic impedance induce reflection and refraction waves of finite amplitudes. These waves, or their reflections, can cause premature ignition, separation before successful ignition, extinction of reaction, or complicate and possibly destroy any beneficial directional effects of the explosive. Prior to this invention, no explosive has been designed so that the composition changes gradually and smoothly (at a finite gradient) from point to point in order to avoid these problems.
The use of multiple optional points when initiating spatially uniform explosive charges has been attempted. For example, multiple ignition points were added to the circumference of a cased cylindrical charge in order to determine whether it is possible to direct a higher percentage of the case fragments towards a target, rather than equally dispersing the fragments in all directions like in traditional warheads. However, when multiple optional ignition points are combined with gradient explosive technology, we can create explosive charges that perform optimally in different missions, even with conflicting requirements on the explosive composition, such as the fragmentation and internal blast requirements explained above.
The invention proposed herein comprises a gradient explosive in association with multiple optional selective ignition points. The novel concept of a gradient explosive refers to an explosive wherein the chemical and physical composition changes gradually from point to point. When an explosive of this nature is combined with multiple optional ignition points, different outcomes can be obtained from detonating the same explosive charge depending on which one of the optional ignition points is used to initiate the charge. Gradient explosives do not present the inherent problems noted above associated when combining two different explosives in the same charge because the gradual change in composition will not generate strong refraction and reflection waves of the detonation wave. Other benefits of gradient explosives not available from current explosive technology are explained below.
First, gradient explosives permit shaping of the detonation wave. The inclination of the detonation wave to the liner of a shaped-charge can be controlled to enhance performance, thereby producing faster, more stable jets. Second, warhead directional effects can be built directly into the explosive itself. Third, because gradient explosives are capable of multiple tasks as noted above, the terminal effect of the explosive can be selected en route to a target. Finally, gradient explosives can perform tasks which prior explosives were incapable of performing, or at least performing well. For example, the detrimental effects of so called corner turning, encountered when a detonation wave is axially transmitted from a smaller to a larger diameter concentric explosive charge, can be eliminated by having the comers, or shoulders of the larger charge, rich with an explosive component that can support a faster detonation wave.
Accordingly, it is the object of this invention to provide an explosive wherein the composition of the explosive changes gradually across the explosive.
It is a further object of this invention to provide an explosive capable of performing multiple, selective tasks.